STP ShaliPlast P
Chloride-free lignosulphonate water reducer that trims the w/c ratio of everyday structural concrete — IS 9103 and ASTM C494 Type A compliant, stocked and supported by Space Arc across Delhi NCR and pan-India.
What is it?
A modified lignosulphonate, normal-setting water-reducing admixture from STP Limited (older specifications may list it as ShaliCon WR), supplied as an amber-brown liquid with nil added chloride.
Where is it used?
Ready-mix, precast, prestressed, lightweight and general structural RCC — from housing and commercial frames to bridge and infrastructure concrete.
Why use it?
It cuts the mixing water needed for a given slump, so the same cement content produces denser, stronger concrete with lower shrinkage and permeability.
How is it applied?
Dosed at 0.2–0.5% by weight of cement into the gauging water — never onto dry cement — ideally through a calibrated dispenser at the batching plant.
About STP ShaliPlast P
ShaliPlast P is the general-purpose plasticiser in STP Limited’s admixture range — the product an RMC plant or site engineer reaches for when an M20 to M35 mix needs workable, pumpable concrete without pushing the water-cement ratio past what the mix design allows. It is built on modified lignosulphonate chemistry with no added chloride ions, which matters in India where nearly every pour involves reinforcement and IS 456 durability clauses. The admixture conforms to IS 9103 as well as ASTM C494 Type A, meaning it is a water-reducing, normal-setting product: at the recommended dose it will not meaningfully accelerate or retard your stripping cycle.
In fresh concrete, ShaliPlast P gives a noticeably more plastic and cohesive mix — easier to place around congested steel, easier to compact, and less prone to bleeding at the shutter face. In the hardened state, the reduced water content translates into higher strength, lower drying shrinkage and a tighter, less permeable matrix. For contractors it is also simply economical: a low dose per cubic metre delivers a measurable strength and durability gain on ordinary structural grades, without the cost of a PCE system the mix may not need. Space Arc supplies it in original STP packing with dosage guidance and trial-mix support.
The technical insight
When cement meets water, the grains carry mixed surface charges and immediately clump into flocs. These flocs trap a share of the mixing water inside them — water that adds nothing to workability but still counts against your w/c ratio. Lignosulphonate polymers in ShaliPlast P adsorb onto the cement grain surfaces and give every particle a similar negative charge. The grains repel one another, the flocs break open, and the trapped water is released to lubricate the mix. The practical result is a choice: hold the water constant and gain slump, or hold the slump constant and remove water — typically in the 5–12% band depending on cement and mix proportions. Because it is a Type A chemistry, dispersion happens without significant set retardation at the correct dose; push past 0.5% and the same molecules begin coating grains heavily enough to delay hydration, which is why overdosing extends setting time sharply.
Where it is used
- Ready-mix concrete production where consistent workability is needed at a controlled w/c ratio
- RCC columns, beams and slabs in residential and commercial building frames (typically M20–M35)
- Bridge and infrastructure concrete where lower permeability and shrinkage improve durability
- Precast elements, where a cohesive mix aids compaction and mould finish
- Prestressed concrete, where nil chloride content protects strands and tendons
- Lightweight concrete mixes that need workability without extra water
- Expansive and mass concrete pours where reduced mixing water limits shrinkage-related cracking
Key advantages
- Reduces mixing water at equal slump — typically 5–12% depending on the mix — improving strength and density
- Nil added chloride, so it is safe for reinforced and prestressed concrete alike
- Tighter, less permeable hardened concrete with reduced drying shrinkage
- More cohesive fresh mix: easier handling, placing, compaction and finishing with less segregation
- Normal-setting at the recommended dose, so formwork and stripping cycles stay predictable
- Compatible with all types of Portland cement, including sulphate-resisting cement (SRC)
- Low dose and low cost per cubic metre make it an economical upgrade for ordinary structural grades
Limitations & considerations
- Water reduction is modest by design; for M40 and above, pumped long-distance mixes or flowing concrete, an SNF or PCE superplasticiser is the correct tool
- Overdosing beyond 0.5% extends setting time severely — dispenser calibration and supervision are essential
- Not compatible with high-alumina cement
- It boosts the efficiency of air-entraining agents, so AEA dosage must be cut back and air content verified when the two are used together
- Shelf life is 9 months in unopened drums, and stock must be kept under shed, away from heat
- Actual water reduction varies with cement brand, fineness and mix proportions — confirm the dose with site trials before production batching
Selection & best practice
Run a trial mix first: start at 0.2% by weight of cement and adjust upward only as the trials justify, staying within the 0.2–0.5% band (roughly 180–450 mL per 100 kg of cement). Always add ShaliPlast P to the gauging water — it must never touch dry cement. A good batching sequence is to charge the aggregates and cement with about 70% of the mixing water, mix for three minutes, then introduce the remaining water carrying the admixture and mix for a further three minutes until the target slump is reached. If the mix design includes other admixtures, dose each one into the mixer separately, never pre-blended in one container. Where an air-entraining agent is specified, reduce its dose and measure air content on the trial batch, since ShaliPlast P increases the AEA’s air-producing efficiency. Store drums sealed, in a cool, dry, shaded area.
Specifications
| Form / Colour | Amber-brown liquid |
| Chemistry | Modified lignosulphonate |
| Specific gravity | 1.14 ± 0.02 |
| pH | 7–8 |
| Chloride content | Nil |
| Dosage | 0.2–0.5% by weight of cement (approx. 180–450 mL per 100 kg cement) |
| Standards compliance | IS 9103; ASTM C494 Type A |
| Packing | 20 kg and 200 kg drums |
| Shelf life | 9 months in original unopened packing, stored cool and dry under shed |
Industry use cases
Ready-Mix Concrete
RMC plants use ShaliPlast P as the base plasticiser for commercial M20–M35 supply — steady workability at the designed w/c ratio, with nil chloride keeping every load safe for reinforced work.
Housing & Commercial Buildings
Contractors on RCC frames get a more cohesive mix that moves through congested column and beam reinforcement, compacts fully and strips on the normal cycle.
Precast & Prestressed Yards
Yards casting girders, planks and poles benefit from the cohesive mix and clean mould finish, while the chloride-free formulation protects prestressing strand.
Bridges & Infrastructure
On decks, piers and substructure concrete, the reduced water content delivers the lower permeability and shrinkage that long-life infrastructure specifications demand.
Lightweight & Specialty Concrete
Lightweight and expansive concrete mixes gain workability without additional water, protecting density targets and dimensional behaviour.
Frequently asked questions
How much ShaliPlast P do I add per 50 kg bag of cement?
Is ShaliPlast P safe for reinforced and prestressed concrete?
What is the difference between ShaliPlast P and a superplasticiser?
What happens if the dose is exceeded?
Which cements and admixtures is it compatible with?
What pack sizes are available and how long does it keep?
How we position STP ShaliPlast P
ShaliPlast P sits at the entry point of STP’s concrete admixture family: it is the economical choice for everyday structural grades, while ShaliPlast SP (SNF-based) and the ShaliPlast PCE series take over where high-grade, pumped or flowing concrete demands greater water reduction. Projects that also need watertightness can pair the mix with STP’s integral waterproofing admixtures rather than stretching a plasticiser beyond its job. Where a consultant’s approved-makes list runs to other brands, Space Arc stocks direct equivalents — most notably Fosroc Conplast P509, the same chloride-free lignosulphonate chemistry, and Conplast SP430 where a superplasticiser is specified. Our team can help you match the admixture to the mix design, not the other way around.
Fosroc Conplast P509 — Specify Conplast P509 when the approved-makes list calls for Fosroc — it is the same chloride-free lignosulphonate plasticiser chemistry, and Fosroc documents particularly good results in fly-ash and slag-blended mixes.
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